Automatic slack adjuster



March 1, 1938. T ss 2,109,637

AUTOMATIC SLACK ADJUSTER Filed Aug. 18, 1936 4 Shets-Sheet 1 fi uawmu M 19% A (la rneya March 1, 1938. H. GUTKAISS AUTOMATIC SLACK ADJUSTER Filed Aug. 18, 1936 4 Sheets-Sheet 2 v M an w m m fl v A". m M. m 1; m a h v V w a fiM a l A 3 Z 4 1 a, f, i: w, M

H. GUTKAISS March 1 1938.

Filed Aug. 18, 1936 4 Sheets-Sheet 3 I ll llllll- 9 v A w l r. A

at... Mar. 1, 1938 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to automatic slack adjusters, and more particularly to a slack adjuster adapted for use in connection with vehicular wheel brakes.

An object of the present invention is to provide a slack adjuster particularly designed for use with air brakes to the end that such brakes will be in proper adjustment at all times.

The invention together with its objects and advantages will be best understood from a study of the following description taken in connection with the accompanying. drawings wherein:-

Figure l is an elevational view illustrating the application of the invention.

Figures 2; 3, and 4 are detail sectional views taken substantially on the lines 2-2, 3-3, and' 4-4 respectively of Figure 5.

Figure 5 is a detail sectional view taken sub stantially on the line 5-5 of Figure 1.

Figure 6 is a fragmentary detail sectional view showing the manner of mounting an eccentric member.

Figure 7 is a fragmentary detail view partly in section and partly in elevation showing the purpose of the eccentric member above referred Figure 8 is a vertical sectional view through the toothed wheels.

Figure 9 is a perspective view of. a vertically shiftable dog.

Figure 10 is a detail sectional view taken substantially on the line lit-I of-Figure 4. Y

Figure 11 is a perspective view of a fixed guide block and Figure 12 is a plan view of a conventional cam shaft.

Referring to the drawings by reference numerals, it will be seen that a conventional vehicular wheel brake is indicated generally by the reference numeral 5. This brake is preferably of the air brake type. Suitably mounted on the axle housing 6 of the vehicle and secured to the axle housing as at l is a casing 8.

A cam shaft 9 is provided with keys II that are received in guides or ways l2 provided internally of the hubs of. toothed wheels I 3 and M, respectively. As will be clear from a study of Figures 3 and 4, the teeth of the wheels l3 and H are reversely directed relative to one another.

The cam shaft 9 has portions thereof suitably journaled in bearings l provided therefor on the housing 8 as shown in Figure 5 and said housing is also provided at the top thereof with a neck N that accommodates the leg portions of the fork IS, the legs of which fork at the ends thereof are suitably provided to accommodate the shaft 9 so that the fork i0 is mounted to rotate about the shaft 9 as an axis.

Suitably associated with the neck lid of the casingis a dust protector ll of any suitable structure and material.

The lever l6 at one end is connected with the usual brake rod l8 in the usual manner,.

\ Pivotally associated with the lever it between the legs thereof as at I9 are oppositely directed dogs 2|, 22 that have toothed ends normally engaged with the teeth of the wheels l9 and I4, respectively, through the medium of suitably provided springs 23 (see Figures 3 and 4). The springs 23 as shown in Figure 3 are suitably connected at one end to the fork It.

It will be understood that one end of the shaft 9 extends into the brake drum 5 and is equipped with a cam (not shown) that is operated to expand the brake shoes or brake band (not shown) so that braking action is secured by frictional engagement by the brake shoes with the brake drum.

Suitably secured on one side wall of the casing 8 through the medium of bolt and nut means 24 is an eccentric or cam disk 25 with which is cooperable a roller 26 suitably mounted on and provided adjacent the toothed end of the dog 22 for raising the toothed end of the dog 22 out of engagement with the toothed wheel I as shown in Figure 7 as the brake is released and for holding the dog 22 in raised position as long as the brake remains released. In Figure '7 lever I9 is shown in a brake-released position.

It will thus be seen that in applying the vehicular wheel brake the lever I6 is caused to swing in a clockwise direction from the position shown in Figure '7 to substantially the position shown in either Figure 2 or Figure 8. Movementof the lever l6 to the position shown in either Figure2 or Figure 3, which is a brakeapplying position, is transmitted through the engagement of the dog 2| with the toothed wheel ll for rotating the cam shaft 9 in a clockwise .direction to turn the cam associated therewith in a proper direction for forcing the brake shoes into frictional contact with the drum of the brake for applying a braking action to the vehicle wheel.

Upon release of the vehicular wheel brake lever l6 moves in a reverse direction, that is to say, in

a counterclockwise direction from the position for releasing the brakemhoes and permitting the same to move out oi i'rictional contact with the brake drum. In this connection it will be appreciated that as the lever It moves to a brake releasing position roller 22 on the dog 22 will engage the cam 25 to raise the dog 22 to the position shown in Figure 7 and outoi emagement with the toothed wheel ll, the dog 22 remaining in the raised position shown in Figure 7 as long as the vehicular wheelbrake remains in a re- I leased condition. In this connection, it will of course be understood that the return movement of the lever I8 is transmitted to the shaft I for releasing the brake through the medium of the dog 22 engaging the toothed wheel I4, the movement of the dog 22 out oi engagement with the toothed wheel H taking place substantially simultaneously with, or slightly prior to the complete release of the vehicular wheel brake.

Thus, it willbe appreciated that the dog 22 and wheel it provide for a positive return of the brake cam to a brake releasing position preclud-' ing the possibility of the cam becoming stuck in applied position. I

As is also thought to be apparent, the above instrumentalities and arrangement thereoi provide for the permitting of the dog 2| -to ratchet one tooth relative to the wheel l2 incidental'to a return of the lever I! to a brake releasing position and as wear on the brake lining takes place. Thus, it will be seen that the extent of movement of lever it to brake applying position will not at any time, regardless of the wear on the brake lining, be in excess of that movement of the lever to brake applying position when the brake lining is unworn or in good condition.

To take up excess slack in the brake mechanism there is also provided a dog 29 of the shape and construction shown in Figure 9. 'I'he dog 22 has a toothed portion engageable with the toothed wheel l3, and a hollow shank portion 20 which accommodates a block 2| which latter, as shown in Figure 10', is pivoted on a bolt 22. It will thus Also, for regulating the relative movement between the dog 29 and the block 3|, there is provided an adjustment screw," that is threaded through the top of the dog 29 and has its inner end arrangedto engage the block 2| to limit the downward movement'of the dog 28 relative to said block.

For securing the screw 22 at the desired position of adjustment, there is suitably secured to one side of the'dog 29 adjacent its upper end a spring 35 which engages the knurled knob oi the screw 34 as also shown in Figure 4.

Also, for urging the toothed endoi the dog'22 into engagement with the teeth. of the wheel i2,

there'is provided a suitably anchored leaf spring "a that bears against the dog 2! in a manner clearly shown in Figure 4.

From the above it will be seen that when the lever I6 is rocked in a clockwise direction for applying the brake and wheel l2 turns therewith in a manner hereinbei'ore explained, dog-20 being engaged with the teeth of wheel i2 will move downwardly and the movement of the dog 29 with the wheel II will be limitedby the .33. mentoi the inner end 0! the adjusting screw 24 with the block 21.- The amount oi movement oi the dog 2| with the wheel" relative to the block II will be substantially equal to the movement of the lever II necessary to apply the brake.

Y Ii and-when the amount oi movement or the extent oi rotationoi the lever II and wheel l2 necessary to actuate the brake is greater than the adjusted space between the block 2| and the inner end of the screw 24, this excess movement or the wheel llwill cause the dog 22 to ratchet one tooth on the wheel i2. Thus, upon return oi. the lever it to a brake releasing position, the rotation of the gear I! inthe direction required .incidentalto a return of the lever II will be arthrough the medium of this invention there is secured at all times a constant stroke in length.

and position or movement of the lever l6 irrespec- Li: 0! the Progressive wear of the shoes or brake It is well known that a brake shoe expanding cam is made in such a manner that it can travel too far and turn completely over. which will lock the wheel fast and many times cause the brake bands to overheat. This takes place especially when the lining is worn and the brakes are in need of attention. In order to prevent this possibility, I have provided a stop screw 21 threaded through the bottom of the casing 2 as shown in Figure 3, and having an inner end working in a groove 22 providedin the periphery of the gear or toothed wheel I in a manner to abut one end wall of the groove 22 for limiting the rotative movement of the wheel II and associated parts and thereby prevent a complete turn-over oi the brake cam and consequently positively insure against overheating oi the worn brake lining. Thus, when the lining has become so worn as to permit the screw 21 to come into play in a manner just described, the operator or the vehicle will know that the brakes are badly in need oi attention.

'Also. to provide access to the dog 2| .withiri the casing 8 for any purpose, as for example to raise the dog 2| out of engagement with the toothed wheel |2, there is provided in the top of the casing I in proximity to the dog 2| an opening for the insertion therethrough of .a screw driver or similar tool. For this opening there is provided a plug P as shown.

Also, to permit access to he had to the adjusting screw 24 for adiusting the latter and to lubricate the same if desired, there is provided in the side of the casing 2 and suitably positioned relative to the dog 20 .a suitable opening for which there is provided a plug P.

Other details of construction] may be mentioned, as for example, the housing 8 may be heavier 'at the side thereof bolted to the axle housing to increase the strength oi the housing at this point.

Also, suitable lubricant fittings may be associated with the bearings I, which fittings 'may a be in the form of grease cups or the libs, and

the casing 8 may be fluid-tight so as to contain a bath of oil or other lubricants to a level approximating the shaft 9.

It is thought that a clear understanding of the construction, utility, and advantages of an invention of this character will be had without a more detailed description.

Having thus described the invention, what is claimed as new'is: 1. In a slack adjuster, the combination with a rotatable shaft, means operable by said shaft for applying a vehicular wheel brake, and a brake fork for rotating said shaft, of a pair of ratchet wheels secured to said shaft, pivoted dogs carried by said fork and engaging the ratchet wheels and movable with the brake lever, means in the path of one of the dogs for moving the latter out of engagement with its ratchet wheel incidental to a. movement of the fork to a brake releasing position, and additional dog means eifective upon wear of the brake lining to engage with the other of the ratchet wheels for holding the same in advance angular position incidental to a return movement of said fork.

2. In a slack adjuster, the combination with a rotatable shaft, means operable by said shaft for applying the brakes, and a fork for rotating the shaft, of a pair of ratchet wheels secured to said shaft, dogs pivotally carried by said fork and engaging said ratchet wheels, a fixed cam member arranged in the path of one'of said dogs, means on said one dog engageable with said cam member for moving said one dog out of engagement with its ratchet wheel incidental to a movement of the fork to a brake releasing position, and additional dog means effective upon wear of the brake lining to engage with the other of ciated with the last-named ratchet wheel to ratchet one tooth so that the amount of move-- ment of the fork need never be in excess of the movement thereof when the lining is unworn.

3. In a slack adjuster, the combination with a rotatable shaft, means operable by said shaft for applying the brakes, and a fork for rotating said shaft, of a pair of ratchet wheels secured to said shaft, dogs carried by said fork and engaging said ratchet wheels for effecting a rotative movement of the ratchet wheels, means for engaging and holding one of the dogs-out of engagement with its ratchet wheel upon movement of the fork to a brake releasing position, and additional dog means for engaging and holding the other of the ratchet wheels in an advance position upon movement of the fork and said ratchet wheels in excess of a predetermined amount.

4. In a slack adjuster, the combination with a rotatable shaft, of a pair of ratchetv wheels rotatable with said shaft, the teeth of the ratchet wheels being reversely directed relative to one another, .a brake applying fork engaged with the shaft to rotate about the shaft as an axis, a dog pivotally connected at one end with said fork cidental to a movement of the fork to a position for releasing the brakes, a dog mounted for sliding movement in a plane tangential to the second ratchet wheel with the rotative'movement of said fork and adapted to ratchet over one tooth on the ratchet wheel when rotative movement of the latter exceeds a predetermined amount, supporting means for the slidably.

mounted dog,- and yieldable means normally urging the slidably mounted dog in one direction.

nanny GU'IKAISS. 

